Alright so i been dealing with this problem for about a month. I have a 08 335xi e90 with ar downpipes, afe intake, jb4. So i have been having it where i would just be driving it down the highway normal and once in a while if i get on it, the car starts to cut out or act like a fullpump going bad issue. Or possibly missfire. I had put it on map 7 with 93 gas and octane booster. It happened on that map and does it on all theres.

I got a smoke test done and have no leaks. I just got spark plugs and what going to check the ones in the car now.

You have installed new plugs or not yet? How many miles on the car? Got a name?

You can also search for "misfire" and read through the typical fixes. 1) install new plugs. 2) move coils, see whether the misfire moves with the coil. 3) possible injector(s), excessive carbon buildup, bad PCV allowing a lot of extra oil into the intake, bad O2 sensors, etc.

Get off map 7 go to map 5. Push DTC once so light is on in the dash, go full power a few times. Odds are JB4 is pulling power becuase your no on race fuel, as well if its surging on power your getting wheel spin and the car itself is pulling power.

I have a buddy on stock turbos still doing this exact same thing but on map 5 with 4 gallons E85/ rest 93 octane. Def check your codes because nothing can be of help without some sort of evidence. If your getting a vibration or hesitation, You probably need new plugs, coil packs, or even maybe bad injectors (see if your car hasnt got injectors installed yet and try and go thru BMW....take your JB4 off just to be safe) If your good with the JB4, try and get a log and send it to Terry or Burger Motorsports and see what they say. Also, map 7 is a RACE GAS map.. 93 with octane booster isnt going to make it to a 100 octane MINIMUM.. I personally havent tried it and dont suggest others to unless they want to have issues, like you are experiencing

Terry is offering a DME reflash done thru Burger Motorsports on COBB tuning DME flash. if your running a strong, consistent E85 mix with 93 octane, you should def try and go this route Car pulls and pulls very nicely without having hiccups or "surges" of power

You can't go by "look". At 25k miles on a tune, it is definitely time to change spark plugs. The electrodes wear down and make it harder to fire the spark. Rounded electrodes bleed electric charge, while flat elctrodes build charge then suddenly spark. Combine that with increased boost, and it is even harder to fire that spark. Something about relative permittivity of the fuel/air mix in the cylinder, I dunno, I'm just talking out of my ass.

Alright im gunna try the plugs i just picked some up see what happens. What if my stock ones are looking good what should i do then?

Recently I had similar symptoms when it got colder.
Started with an occasional sputter/pause, then finally got a misfire code on cylinder #6.
Changed all my plugs (had 1.5 years on them) and swapped cyl #6 coil to cyl #1 just in case.

Problem went away for a week and then it came back.
Single sputter, but no codes, since I instinctively let off whenever I felt something.
The DME needs to register multiple consecutive misfires in order to throw a code,
so I did a long 5th gear pull and finally got multiple misfires that registered a code for cyl #1 this time.

So for me it ended up being the coil, which I replaced the next day and have been fine so far. YMMV.